Mobile communication devices have become increasingly common in current society. The prevalence of these mobile communication devices is driven in part by the many functions that are now enabled on such devices. Increased processing capabilities in such devices means that mobile communication devices have evolved from being pure communication tools into sophisticated mobile multimedia centers that enable enhanced user experiences.
The redefined user experience depends on higher data rates offered by new generation wireless communication systems such as a fifth-generation (5G) system. The new generation wireless communication systems typically employ linear modulation schemes, such as quadrature amplitude modulation (QAM), in conjunction with orthogonal frequency division multiplexing (OFDM) and broad bandwidth (e.g., ≥400 MHz) for achieving the higher data rates and spectrum efficiency. Accordingly, a wireless communication signal communicated in the new generation wireless communication system can correspond to a non-constant amplitude envelope and exhibit higher peak-to-average ratio (PAR). Generally speaking, the higher the data rate the wireless communication signal can achieve, the higher the PAR the wireless communication signal will exhibit.
To achieve the higher data rates and desirable coverage range, the mobile communication device typically employs a broadband power amplifier (PA) to increase output power of the wireless communication signal to maintain sufficient energy per bit and/or desirable signal-to-noise ratio (SNR). Notably, a higher peak associated with the wireless communication signal can cause the broadband PA to move toward compression that can lead to undesirable out-of-band spectral regrowth and in-band distortion. As such, the broadband PA may be configured to operate with a sufficient back-off (e.g., in class-A mode) from the peak to help improve linearity performance of the PA. However, the improved linearity performance is often achieved at the expense of reduced PA efficiency. For example, a wireless communication signal communicated in the 5G system can exhibit a PAR as high as 11 dB. In this regard, it may be necessary to configure a 5G PA to operate with 11 dB back-off. As a result, the 5G PA may be forced to operate at as low as 5% PA efficiency.
Although it may be possible to improve PA efficiency by configuring the PA to operate in a class-AB mode, such an approach can also compromise the linearity performance of the PA. Moreover, the PA may suffer so-called memory effect, in which an instantaneous output power of the PA depends not only on an instantaneous input power of the PA, but also on the historical input powers of the PA. As such, it may be desirable to achieve a good balance between PA linearity and PA efficiency in a broadband PA, while avoiding the so-called memory effect in the broadband PA.